The American Boat & Yacht Council, Inc. of Connecticut (US) published in 1994 a set of standards for which voluntary compliance has been recommended for boat products constructed after Sep. 1, 1996. Within these standards, under section H-31, there is provided recommended seat structure standards and tests for determining whether those standards are met with a particular design.
These standards set out in the 1994 publication include the following definitions:
Adjustable Seat--a permanently installed seat designed to allow the occupant to adjust the seat position vertically and/or horizontally (fore and aft and/or laterally). PA1 Locking Mechanism--a mechanism designed to resist fore and aft, lateral, vertical and rotational movement of the seat. PA1 Permanently Installed--seats whose base or attaching system is permanently attached to the hull or a hull structure. Seats that are readily removable from a permanently installed base or attaching system are considered permanently installed. PA1 Positive Locking Mechanism--a mechanism which relies on mechanical interference or the use of gas springs to prevent fore or aft, lateral, vertical and rotational movement of the seat. PA1 NOTE: Friction devices are not considered mechanical interference locks. PA1 Positive Locking Swivel--relies on positive mechanical inference, not friction, to lock the seat in position. PA1 Readily Removable--capable of removal without the use of tools. PA1 Swivel Seat--a seat designed to rotate about a vertical axis. PA1 Type A Seat--a seat designed for occupancy while the vessel is underway at any boat speed. PA1 Type B Seat--a seat designed for occupancy only at boat speeds not exceeding five miles per hour. PA1 (1) H-31-.7: Type A adjustable seats. PA1 (2) H-31-.7.1: All type A adjustable seats shall employ a locking mechanism for each plane or axis of movement. PA1 (3) H-31-.7.3: Seat swivel locking mechanisms, when locked, shall not rotate relative to the seat base when subjected to a torque of 30 foot pounds (41 N.multidot.m). PA1 (4) H-31-.7.4: Seats with a vertical adjustable feature shall have a positive locking mechanism. (emphasis added) PA1 (5) H-31.7.6: Operator's Swivel Seats with a vertical adjustment feature shall have a positive locking mechanism. PA1 (6) H-31.7.6.1: All operator's seats shall have positive locking swivels that permit the seat to be locked in the intended position and capable of withstanding 150 foot pounds (205 N.multidot.m) of torque. PA1 (7) 31.7.6.2: All seats interchangeable with the operator's seat must meet the requirements of this section. PA1 (1) Type A (Operator)--(Swivel seat capable of withstanding 150 ft-lbs (205 N.multidot.m) of torque). PA1 (2) Type A (passenger)--(Swivel seat capable of withstanding 30 ft-lbs (41 N.multidot.m) of torque). PA1 (3) Type B (seats designed for boats not to exceed 5 mph)--(no standard provided seat can freely rotate due to low speed).
These standards also provide guidelines that are based on whether the seat is a type A (passenger) seat, a type A (operator's) seat or a type B seat. The guidelines include the following:
The ABYC standards can also be summarized as follows with respect to torsion strength requirements.
There exists in the prior art an air adjustable "Power Rise".TM. seat assembly which is available from Springfield Marine Company of Nixa, Mo. The "Power Rise".TM. air spring system features a swivel seat mount that is supported on a stem which is inserted within a cylindrical post and has a hollow cavity for receiving a piston and piston stem with the latter being free to rotate, but fixed axially with respect to the post. The stem includes a spring biased valve at its top positioned within the swivel seat mount. Upon depressing the valve with a shifting lever, the seat can be shifted vertically down or raised to the desired level (under the power of compressed air) where, upon the operator returning the shifting lever to a valve closed position, the spring seat is locked at the desired height.
Based on the above guidelines, a positive locking mechanism can be represented by a gas spring such as the "Power Rise".TM. adjustable vertical height gas spring discussed above. Accordingly, with respect to vertical axis movement, the "Power Rise".TM. air spring system satisfies the above quoted guideline "H-3-7.4" for Type A adjustable (passenger) seats as the air spring is considered a positive locking mechanism for vertical movement. However, because the "Power Rise".TM. air spring system freely rotates, it is not in conformance with the recommended guideline H-31-.7-.1 which requires a locking mechanism for each plane or axis of movement. Thus, the "Power Rise".TM. spring systems are primarily designed for use in Type B settings. Further, any rotational locking mechanism, to be sufficient for Type A (passenger) seats is required to satisfy the recommended guideline of H-31-.7.3 requiring torque resistance of 30 ft-lbs (41 N.multidot.m).
In co-pending application Ser. No. 08/682,189 to Mike Mawhiney, filed on Jul. 17, 1996, there is described a rotation locking assembly which utilizes a cam-activated friction clamp to lock by friction the telescoping inner cylinder of a Power Rise.TM. seat assembly. This friction clamp is sufficient to satisfy the 30 foot-pounds or (41 N.multidot.m) standard set out in H-31-.7.3. The system in application Ser. No. 08/682,189 therefore makes possible the use of a vertical air spring system for Type A adjustable seats and thus allowed for the first time the use of a Power Rise.TM. seat assembly other than in a Type B seat assembly.
However, the seat assembly system described in application Ser. No. 08/682,189, because it relies on a friction lock and also because that friction lock is not specifically designed to withstand 150 foot-pounds (205 N.multidot.m), is not intended to provide a seat assembly support system that satisfies H-31.7.6.1 under the operator's swivel seat heading. Accordingly, due to H-31.7.6.2, which requires all seats to satisfy the operator's seat standard when an interchangeable operator's seat is involved, the operator's seat had to be non-interchangeable with respect to the Type A adjustable passenger seats.
Furthermore, while the friction lock mechanism in application Ser. No. 08/682,189 is in a locked state, to prevent rotation during +5 mph travel, the telescoping inner cylinder is vertically locked with respect to the other cylinder so as to lose the benefits of an air cushion ride made possible by an air spring system. That is, the aforementioned Power Rise.TM. system, in addition to allowing vertical adjustment through manipulation of a lever, also provides a one to two inch cushion effect due to compression of the fluid held by the inner cylinder when the valve is locked. The fact that the friction lock in application Ser. No. 08/682,189 is applied for travel in excess of 5 mph, means that the cushion ride advantage made possible by an air spring is non-operational at a time when most needed (i.e., higher speed travel).